Pontiac FIREBIRD 1972 Service Manual page 490

TANDEM DIAPHRAGM POWER BRAKE-MORAINE 5D-13
PISTON
Fig. 5D-15 Installing Control Valve and Retainer
fecting output of the tandem power brake are
very critical. In order to maintain correct
power brake output, the po wer piston assembly
must begaged for selective fit of reaction piston
whenever the primary po werpiston and/or sec-
ondary
PO
werpiston are replaced during servic-
ing. This gaging operation is not required
if
neither po wer piston is replaced during servic-
ing.
10. The gaging procedure is to be performed as follows:-
(Fig. 5D-17).
a.
and-tighten
the secondary power piston to the
primary power piston without installing the air
RING
Fig. 5D-16 Installing Snap Ring on Air Valve
POWER PISTON GAGING
REMOVE RUBBER REACTION DISC, PISTON
R O D RETAINER & AIR VALVE
SPRING FOR G A G I N G
SECONDARY
CORRECT
'
N O
AIR VALVE-PUSH G O
ROD ASSEMBLY
(REACTION (REACTION
PISTON PISTON
T O O SHORT) T O O L O N G )
Fig. 5D-17 Gaging Reaction Piston
valve spring. (The air valve-pushrod assembly
should be secured to the primary power piston as
described in step 8.)
b. Insert the reaction piston into its cavity in the
secondary power piston. This is accomplished by
placing reaction piston, small diameter first,
through large cavity and into smaller cavity.
c. With secondary power piston up, push on reac-
tion piston to insure that it is seated on air valve.
d. Place gage J 23327 in secondary power piston so
that outer edges rest on bottom of large cavity,
and center section of gage rests over "nose" of
reaction piston. Both ends of gage must be used
to perform gaging operation.
e. Move gage to left or right of "nose" on reaction
piston. Reaction piston is correct length if "nose"
of piston hits "NO GO" level of gage and clears
"GO" level of gage, while outer edges of gage
remain seated on larger cavity of secondary
power piston.
NOTE: If reaction piston is too long, "GO"
level ofgage willnot clear 'hose" without mov-
ing outer edges of gage o f f the seat in large